Tooth decay or dental caries is one of the most common infectious diseases affecting nine out of ten individuals worldwide with higher rates among underprivileged groups. The role of oral biofilm member Streptococcus mutans in the etiology of dental caries has been well established. Management of S. mutans levels in the oral biofilm would therefore be beneficial for oral health and prevent caries development. This project focuses on the eukaryotic-like Ser/Thr protein kinase PknB as an anti-S. mutans target. PknB is an important sensor of envelope related stress and triggers a respective cellular response to increase S. mutans stress resistance. Recently, we were able to demonstrate the increased susceptibility of a PknB deficient strain towards ecological stress. The goal of the present study is to identify an optimal approach to interfere with PknB dependent stress adaptation. In Aim 1 we propose to determine the levels of pknB expression and localization of PknB in the context of biofilm growth. With this approach we will obtain important information about S. mutans biofilm specific gene expression and identify accessible structural targets in PknB. In Aim 2 we will also identify downstream PknB kinase substrates and determine the phosphorylation cascade to identify potential additional intracellular targets for S. mutans specific PknB interference. This study will expand the knowledge of PknB dependent regulation and help to develop possible novel therapeutic strategies to prevent caries. PUBLIC HEALTH RELEVANCE: Dental caries is a common infectious disease causing considerable discomfort in affected individuals. The etiological role of Streptococcus mutans in caries development has been well documented. This project investigates a specific component of S. mutans stress response with the goal of determining the optimal approach to interfere with the stress adaptation process. A detailed understanding of this process will provide important new information for S. mutans specific interventions to prevent dental caries.